We have been testing for the presence of growth factors in the cerebral spinal fluid (CSF) of normal and schizophrenic human subjects. The test system uses neurite growth in cells from a neuroblastoma cell line (Neuro 2-A) to assay the presence of growth factors. Indirect growth factors that cause cells to secrete a diffusible growth substance have been demonstrated. However, the distribution does not discriminate between normal and schizophrenic subjects in specimens tested so far.